Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
Records 1-19 (of 19 Records) |
Query Trace: Boylan A [original query] |
---|
HIV viral load scale-up among children and adolescents: Trends in viral load suppression, sample type and processing in 7 PEPFAR countries, 2015-2018
Hrapcak S , Pals S , Itoh M , Peters N , Carpenter D , Hackett S , Prao AK , Adje-Toure C , Eboi E , Mutisya I , Nyabiage Omoto L , Ondondo RO , Bowen N , Nyanya W , Kayira D , Kaba MD , Mwenda R , Deus MI , Almeida J , Cuco RMM , Boylan A , Beard S , Ashikoto S , van Rooyen G , Kindra G , Diallo K , Carmona S , Nazziwa E , Mwangi C , Ntale J , Ssewanyana I , Nabadda SN , Nabukenya M , Ellenberger D , Rivadeneira E . Pediatr Infect Dis J 2023 42 (4) e102-e104 HIV-positive children and adolescents face gaps in viral load (VL) testing. To understand trends in pediatric/adolescent VL testing, 7 countries collected data from Laboratory Information Management Systems. Results showed increasing proportion of VL tests done through dried blood spot (DBS) and decreased sample rejection rates for DBS compared with plasma, supporting use of DBS VL when skilled phlebotomy is unavailable. |
Stability of specimens for use in the Centers for Disease Control and Prevention assays for factor VIII and IX inhibitors
Payne AB , Boylan B , Niemeyer G , Werner B , Driggers J , Miller CH , Bean CJ . Res Pract Thromb Haemost 2022 6 (7) The Centers for Disease Control and Prevention (CDC) Nijmegen‐Bethesda Assay (NBA)1 is a modification of traditional methods2., 3. for measurement of factor VIII (FVIII) and factor IX (FIX) inhibitors that includes a 30‐minute preanalytical heat treatment (PHT) step to remove endogenous and infused FVIII or FIX. Specimens for inhibitor tests using PHT thus do not require the stringent conditions needed to maintain clotting factors during shipping and storage, as we have previously documented by split‐sample analysis showing that results of the CDC‐modified NBA on specimens shipped cold correlated well with those of frozen specimens.1 |
Cervical cancer screening and treatment, HIV infection, and age: Program implementation in seven regions of Namibia
Korn AK , Muzingwani L , O'Bryan G , Ensminger A , Boylan AD , Kafidi EL , Kashali M , Ashipala L , Nitschke AM , Dziuban EJ , Forster N , Eckert LO , O'Malley G . PLoS One 2022 17 (2) e0263920 The aim of this study was to assess differences in cervical cancer screening and treatment outcomes by HIV status in a routine programmatic setting with a high generalized HIV prevalence. Women living with HIV (WLHIV) are at heightened risk of developing cervical cancer and the World Health Organization recommends all WLHIV who are sexually active be screened, regardless of age. In 2018, Namibia's Ministry of Health and Social Services introduced a screen-and-treat approach using visual inspection with acetic acid (VIA) and ablative treatment with cryotherapy or thermocoagulation with a focus on screening HIV-positive women due to Namibia's 11.5% prevalence of HIV in women aged 15-49. Using program data from October 2018 to March 2020 from seven of the country's 14 regions, we calculated descriptive statistics and chi-square tests to test the statistical significance of differences in VIA-positivity, ineligibility for ablative treatment, treatment completion, and same day treatment completion by HIV status. Between October 2018 and March 2020, the program conducted 14,786 cervical cancer screenings. Among 8,150 women who received their first VIA screening, more WLHIV screened VIA-positive (17%) than HIV-negative women (15%). This difference was statistically significant (p = 0.02). Among 2,272 women who screened VIA-positive at any screening, 1,159 (82%) completed ablative treatment. This suggests ablative treatment is feasible and acceptable in resource-limited settings. WLHIV were also more likely to complete treatment than HIV-negative women (p<0.01). Differences in health seeking behavior of sub-populations as well as resource availability between service delivery points should be considered for further investigation. Going forward in order to strengthen program implementation and expand screening access and uptake further investigation is needed to determine cancer incidence by HIV status, age, and time since last screening to assess cases that are averted as well as potential rates of overtreatment. |
The chromogenic Bethesda assay and the Nijmegen-Bethesda assay for factor VIII inhibitors in hemophilia A patients: Are they equivalent
Miller CH , Boylan B . J Thromb Haemost 2021 19 (7) 1835-1837 We previously described in this journal a modified Nijmegen-Bethesda assay (NBA) for factor VIII (FVIII) inhibitors in hemophilia A (HA) that uses preanalytical heat inactivation of infused or endogenous FVIII to allow inhibitor measurement postinfusion1 and compared that assay with a chromogenic Bethesda assay (CBA) that is identical except for use of an FVIII chromogenic substrate assay (CSA) rather than a one-stage assay (OSA) as the endpoint for inhibitor detection.2 Our primary focus was on use of the CBA as a confirmatory test for low positive NBA results. Introduction of the non-FVIII treatment product emicizumab (Hemlibra) has brought increased interest in inhibitor assays using CSA because emicizumab interferes with the OSA and thus with Bethesda assays for FVIII inhibitors using the OSA.3-5 CSA for FVIII that use bovine factor X (FX) are insensitive to emicizumab,5 and a CBA using such CSA has been successfully used for inhibitor testing in its presence.6, 7 Clinical laboratories providing inhibitor testing have the option of maintaining two inhibitor assays and choosing the correct one for each patient depending on the product used or switching to a CBA to accommodate testing on all patients. Clinical adoption of a new assay methodology requires demonstration that the new method is equivalent to the old. Recent reexamination of the dataset of paired NBA and CBA results from our original paper2 revealed differences that may influence such comparisons and that, if not considered, could hinder validation of the CBA for clinical use. |
Evaluation of anti-factor VIII antibody levels in patients with haemophilia A receiving immune tolerance induction therapy or bypassing agents
Boylan B , Niemeyer GP , Werner B , Miller CH . Haemophilia 2020 27 (1) e40-e50 INTRODUCTION: Bleeding episodes in patients who have haemophilia A (HA), a hereditary bleeding disorder caused by a deficiency in factor VIII (FVIII), are treated or prophylactically prevented with infusions of exogenous FVIII. Neutralizing antibodies, referred to as inhibitors, against infusion products are a major complication experienced by up to 30% of patients who have severe HA. Bypassing agents (BPA), a class of therapeutics given to patients who have inhibitors, bypass the need for FVIII in the coagulation cascade, and long-term inhibitor eradication is accomplished using immune tolerance induction therapy (ITI). Data examining the antibody levels in patients receiving BPA and ITI are limited. AIM: Measure anti-FVIII antibody levels in specimens from patients receiving ITI or BPA in order to evaluate the anti-FVIII antibody response in those patients. METHODS: Specimens were tested using the CDC-modified Nijmegen-Bethesda assay (NBA) and the CDC fluorescence immunoassay (FLI) for anti-FVIII IgG(1) and IgG(4) . RESULTS: NBA-negative specimens from patients undergoing ITI or receiving BPAs have a higher frequency of anti-FVIII IgG(4) positivity compared with the previously published level for NBA-negative HA patients. Analysis of anti-FVIII antibody levels in serial samples from patients undergoing ITI reveals that antibodies can persist even after the patient's NBA result falls into the negative range. CONCLUSIONS: Measurement of anti-FVIII antibodies may be a useful means to better contextualize NBA results in specimens from patients receiving BPA or ITI. In addition, assessment of anti-FVIII antibody levels has the potential to improve inhibitor surveillance and clinical decision-making related to the progress of ITI. |
Validation of the chromogenic Bethesda assay for factor VIII inhibitors in hemophilia a patients receiving emicizumab
Miller CH , Boylan B , Payne AB , Driggers J , Bean CJ . Int J Lab Hematol 2020 43 (2) e84-e86 Development of antibodies interfering with the function of factor VIII (FVIII) replacement products is one of the most significant complications in the treatment of hemophilia A (HA). Laboratory testing for such antibodies, called inhibitors, is an important part of hemophilia care and is conducted both to identify the cause of treatment failure and as routine screening to detect early antibody appearance. Treatment of HA patients who develop inhibitors is often carried out by giving repeated doses of FVIII to induce immune tolerance and allow use of FVIII or by use of by-passing agents that act by facilitating coagulation without the need for FVIII. The newest by-passing product, emicizumab (Hemlibra®), is a bispecific antibody that mimics the function of FVIII by bringing factor IXa and factor X (FX) together to produce the Xa complex.1,2 Emicizumab, which is long acting and given subcutaneously, is now widely available for use in patients both with and without inhibitors to avoid frequent use of intravenous FVIII replacement. |
Rapid Adaptation of HIV Treatment Programs in Response to COVID-19 - Namibia, 2020.
Hong SY , Ashipala LSN , Bikinesi L , Hamunime N , Kamangu JWN , Boylan A , Sithole E , Pietersen IC , Mutandi G , McLean C , Dziuban EJ . MMWR Morb Mortal Wkly Rep 2020 69 (42) 1549-1551 Namibia is an upper-middle income country in southern Africa, with a population of approximately 2.5 million (1). On March 13, 2020, the first two cases of coronavirus disease 2019 (COVID-19) in Namibia were identified among recently arrived international travelers. On March 17, Namibia's president declared a state of emergency, which introduced measures such as closing of all international borders, enactment of regional travel restrictions, closing of schools, suspension of gatherings, and implementation of physical distancing measures across the country. As of October 19, 2020, Namibia had reported 12,326 laboratory-confirmed COVID-19 cases and 131 COVID-19-associated deaths. CDC, through its Namibia country office, as part of ongoing assistance from the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) provided technical assistance to the Ministry of Health and Social Services (MoHSS) for rapid coordination of the national human immunodeficiency virus (HIV) treatment program with the national COVID-19 response. |
Neonatal seizures: Case definition & guidelines for data collection, analysis, and presentation of immunization safety data
Pellegrin S , Munoz FM , Padula M , Heath PT , Meller L , Top K , Wilmshurst J , Wiznitzer M , Das MK , Hahn CD , Kucuku M , Oleske J , Vinayan KP , Yozawitz E , Aneja S , Bhat N , Boylan G , Sesay S , Shrestha A , Soul JS , Tagbo B , Joshi J , Soe A , Maltezou HC , Gidudu J , Kochhar S , Pressler RM . Vaccine 2019 37 (52) 7596-7609 Seizures are the most common neurological emergency in newborns and can be associated with significant mortality and neuro-developmental disability. Neonatal seizures are a major challenge for clinicians because of inconspicuous clinical presentation, variable electro-clinical correlation, and poor response to antiseizure drugs. It is well recognized that fever and infection can trigger seizures in young children and that this risk is enhanced in children with epilepsy. As immunization may cause a fever, vaccination can be a non-specific trigger for seizures in children [1]. On the other hand, children with epilepsy do not appear to be at increased risk of seizures following immunization [2]. It is unclear whether vaccination in newborns or maternal vaccination, is associated with a higher risk of neonatal seizures. However, as maternal immunization with established vaccines becomes more prevalent across multiple geographies, and new maternal vaccine candidates enter late-stage development, it is becoming increasingly important to create easily adopted standard definitions for adverse events potentially associated with these interventions. The Brighton Collaboration has previously published a case definition for seizures in children [3] but not for seizures in neonates. |
Reagent substitution in the chromogenic Bethesda assay for factor VIII inhibitors
Payne AB , Miller CH , Ellingsen D , Driggers J , Boylan B , Bean CJ . Haemophilia 2019 25 (5) e342-e344 The Nijmegen-Bethesda assay (NBA) is the gold standard for measurement of factor VIII (FVIII) inhibitors in haemophilia A patients.1 Modification of the traditional NBA2 to use a chromogenic measurement of FVIII as the endpoint is necessary for measurement of FVIII inhibitors in the presence of heparin, lupus anticoagulants, or by-passing agents such as emicizumab, due to their interference in clot-based assays.3–5 Parallel testing has shown this modification to produce similar results to the NBA in the absence of these interfering substances.6 In the clot-based NBA, substitution of imidazole-buffered bovine serum albumin (IB-BSA) for FVIII-deficient plasma (FVIIIDP) as diluent in control mixtures and specimen dilutions has been shown to produce equivalent results when the threshold for positivity was slightly adjusted.7 This study aims to evaluate a similar substitution in the chromogenic Bethesda assay (CBA) and to describe the performance characteristics of this modified assay. |
Distinguishing lupus anticoagulants from factor VIII inhibitors in haemophilic and non-haemophilic patients
Rampersad AG , Boylan B , Miller CH , Shapiro A . Haemophilia 2018 24 (5) 807-814 INTRODUCTION: Accurate diagnosis of an inhibitor, a neutralizing antibody to infused factor VIII (FVIII), is essential for appropriate management of haemophilia A (HA). Low-titre inhibitors may be difficult to diagnose due to high rates of false-positive inhibitor results in that range. Transient low-titre inhibitors and false-positive inhibitors may be due to the presence of a lupus anticoagulant (LA) or other non-specific antibodies. Fluorescence immunoassay (FLI) to detect antibodies to FVIII is a sensitive method to identify inhibitors in HA. Evaluations of antibody profiles by various groups have demonstrated that haemophilic inhibitors detected by Nijmegen-Bethesda (NBA) and chromogenic Bethesda (CBA) assays correlate with positivity for anti-FVIII immunoglobulin (Ig) G1 and G4. AIM: This study sought to determine whether FLI could distinguish false-positive FVIII inhibitor results related to LAs from clinically relevant FVIII inhibitors in HA patients. METHODS: Samples from haemophilic and non-haemophilic subjects were tested for LA, specific FVIII inhibitors by NBA and CBA, and anti-FVIII immunoglobulin profiles by FLI. RESULTS: No samples from LA-positive non-haemophilic subjects were positive by FLI for anti-FVIII IgG4. Conversely, 91% of NBA-positive samples from haemophilia subjects were positive for anti-FVIII IgG4. Two of 11 haemophilia subjects had samples negative for anti-FVIII IgG4 and CBA, which likely represented LA rather than FVIII inhibitor presence. CONCLUSIONS: Assessment of anti-FVIII profiles along with the CBA may be useful to distinguish a clinically relevant low-titre FVIII inhibitor from a transient LA in HA patients. |
Reagent substitutions in the Centers for Disease Control and Prevention Nijmegen-Bethesda assay for factor VIII inhibitors
Miller CH , Payne AB , Driggers J , Ellingsen D , Boylan B , Bean CJ . Haemophilia 2018 24 (3) e116-e119 The Nijmegen-Bethesda assay (NBA), considered the “gold standard” for measurement of factor VIII (FVIII) inhibitors in haemophilia A,1 introduced two modifications to the traditional Bethesda assay (BA) for stabilization during the 2-hour incubation at 37°C: (i) buffering of normal pooled plasma (NPP) in the test and control mixtures with imidazole and (ii) substitution of FVIII-deficient plasma (FVIIIDP) for imidazole buffer (IB) in the control mixture and for specimen predilution.2 The NBA has not been widely adopted in the United States, because of the increased cost incurred by use of FVIIIDP rather than buffer and the lack of FDA-approved commercial reagents.3 Surveys of North American coagulation laboratories have shown that only 20% use the NBA, 70% use buffered NPP in a “hybrid” of the NBA and BA, and one-third use diluents other than those recommended in published methods.3 This lack of methodological uniformity may partially account for poor interlaboratory reproducibility, a well-known problem with FVIII inhibitor testing.3 |
Effects of pre-analytical heat treatment in factor VIII (FVIII) inhibitor assays on FVIII antibody levels
Boylan B , Miller CH . Haemophilia 2018 24 (3) 487-491 INTRODUCTION: The use of pre-analytical heat treatment (PHT) with the Nijmegen-Bethesda assay (NBA) for inhibitors to factor VIII (FVIII) can remove/destroy infused or endogenous FVIII from patient plasma samples, allowing testing of recently infused patients with haemophilia. Two PHT methods have been described as follows: heating to 56 degrees C for 30 minutes and heating to 58 degrees C for 90 minutes. Data examining the effects of PHT on anti-FVIII IgG4 , the antibodies known to correlate most closely with the presence of FVIII inhibitors, are limited. AIM: To assess the effect of PHT on the levels of detectable anti-FVIII IgG4 . METHODS: Nijmegen-Bethesda assay-positive specimens were incubated at 56, 58 or 60 degrees C for 90 minutes, and anti-FVIII IgG4 was measured by fluorescence immunoassay (FLI) at 30-minute intervals. The effects of PHT on the ability of recombinant FVIII (rFVIII) to inhibit detection of patient antibodies by FLI was also examined to assess the stability of rFVIII under the various PHT conditions tested. RESULTS: Levels of anti-FVIII IgG4 showed little change following incubations at 56 degrees C (mean 101% of original value at 30 minutes and 100% at 60 minutes) but decreased upon exposure to 58 degrees C (mean 85% at 30 minutes and 66% at 60 minutes). In addition, heating to 56 degrees C effectively decreased the ability of rFVIII to block antibody binding compared to unheated rFVIII. CONCLUSION: The optimal temperature for PHT in the FVIII NBA is 56 degrees C. Higher temperatures may lead to loss of inhibitory antibodies. |
Limit of detection and threshold for positivity of the Centers for Disease Control and Prevention assay for factor VIII inhibitors
Miller CH , Boylan B , Shapiro AD , Lentz SR , Wicklund BM . J Thromb Haemost 2017 15 (10) 1971-1976 BACKGROUND: The Bethesda assay (BA) for measurement of factor VIII (FVIII) inhibitors called for quantitation of positive inhibitors using dilutions producing 25-75% residual activity (RA), corresponding to 0.4-2.0 Bethesda units, recommending use of "more sensitive methods" for samples with RA closer to 100%. The Nijmegen modification (NBA) changed the reagents used but not these calculations. Some specimens negative by NBA have been shown to have FVIII antibodies detectable by sensitive immunologic methods. OBJECTIVE: To examine the performance at very low inhibitor titers of the Centers for Disease Control and Prevention (CDC)-modified NBA (CDC-NBA), which includes preanalytical heat inactivation to liberate bound anti-FVIII antibodies. METHODS: Specimens with known inhibitors were tested by CDC-NBA. IgG4 anti-FVIII antibodies were measured by fluorescence immunoassay (FLI). RESULTS: Diluted inhibitors showed linearity below 0.4 Nijmegen-Bethesda units (NBU). Using 4 statistical methods, the limit of detection of the CDC-NBA was determined to be 0.2 NBU. IgG4 anti-FVIII antibodies, which correlate most strongly with functional inhibitors, were present at rates above the background rate of healthy controls in specimens with titers ≥0.2 NBU and showed an increase in frequency from 14.3% at 0.4 NBU to 67% at the established threshold for positivity of 0.5 NBU. CONCLUSIONS: The CDC-NBA can detect inhibitors down to 0.2 NBU. The FLI, which is more sensitive, demonstrates anti-FVIII IgG4 in some patients with negative (<0.5) NBU. The sharp increase in IgG4 frequency between 0.4-0.5 NBU validates the established threshold for positivity of ≥0.5 NBU for the CDC-NBA, supporting the need for method-specific thresholds This article is protected by copyright. All rights reserved. |
Alcohol and cocaine use among Latino and African American MSM in 6 US cities
Zaller N , Yang C , Operario D , Latkin C , McKirnan D , O'Donnell L , Fernandez M , Seal D , Koblin B , Flores S , Spikes P . J Subst Abuse Treat 2017 80 26-32 Gay, bisexual, and other men who have sex with men (MSM) are disproportionately affected by HIV. MSM comprise roughly 2% of the US population, yet approximately two-thirds of new HIV infections are among MSM (Centers for Disease Control and Prevention, 2016). Additionally, significant racial and ethnic disparities exist with respect to HIV transmission among MSM. Based on the current HIV diagnoses rates in the US, about 1 in 2 African American men who have sex with men (AAMSM), 1 in 4 Latino MSM (LMSM) and 1 in 11 white MSM will be diagnosed with HIV during their lifetime (Center for Disease Control and Prevention (CDC), 2016a). In general, substance-using MSM are among the groups with the greatest risk for HIV infection (Centers for Disease Control and Prevention, 2011; Margolis, Joseph, Hirshfield, et al., 2014; Pines, Gorbach, Weiss, et al., 2014; Plankey, Ostrow, Stall, et al., 2007); nearly a third of incident HIV infections among MSM may be associated with non-injection drug use (Mansergh et al., 2008; Van Tieu & Koblin, 2009). Substance-using sexual minorities are more likely to underutilize substance use treatment (McCabe, Bostwick, Hughes, West, & Boyd, 2010) and may be an HIV transmission bridge to non-drug-using populations (Lambert et al., 2011). | With respect to alcohol use, high rates of both alcohol consumption and binge drinking have been documented among MSM populations (Finlayson et al., 2011). Additionally, previous studies have found associations between heavy drinking, as define as having 6 or more drinks on one occasion or 4 or more drinks daily, and HIV risk behaviors among MSM, such as condomless anal intercourse and greater number of sexual patterns (Colfax et al., 2004; Greenwood et al., 2001; Koblin et al., 2003a; Woolf & Maisto, 2009). Previous studies also suggest that many substance-using MSM populations engage in use of multiple substances, often concomitantly (Santos et al., 2013). There also may be a dose response with number and frequency of substances used with respect to condomless anal sex among HIV negative MSM (Santos et al., 2013). However, patterns of substance-use vary across racial and ethnic MSM populations, e.g. African American substance-using MSM being more likely to use crack/cocaine relative to other substance-using MSM populations (Goldstein, Burstyn, LeVasseur, & Welles, 2016; Halkitis & Jerome, 2008; Hatfield, Horvath, Jacoby, & Simon Rosser, 2009; Mimiaga, Reisner, Fontaine, et al., 2010; Paul, Boylan, Gregorich, Ayala, & Choi, 2014). Thus, it is important to better understand patterns of concomitant substance-use, e.g. methamphetamine, crack/cocaine and alcohol, across specific sociodemographic categories among MSM populations (Santos et al., 2013). Sociodemographic characteristics which may be particularly relevant for specific MSM populations include poverty and history of incarceration. For example, pronounced racial disparities have been found between AAMSM and other MSM populations with respect to structural barriers, such as low income, unemployment and incarceration, associated with HIV infection (Millet, Peterson, Flores, Hart, et al., 2012). Additionally, a recent study conducted by Rutledge et al, found a high proportion of MSM reporting both a history of incarceration and substance use. This study found rates of incarceration highest among men who classified themselves as “down-low”, e.g. endorsing secrecy about same-sex sexual behavior, promting the authors to posit that this population may engage in trading sex for money more often and thus increase their risk for incarceration (Rutledge, Jemmott, O'Leary, & Icard, 2016). |
Survey of the anti-factor IX immunoglobulin profiles in patients with hemophilia B using a fluorescence-based immunoassay
Boylan B , Rice AS , Neff AT , Manco-Johnson MJ , Kempton CL , Miller CH . J Thromb Haemost 2016 14 (10) 1931-1940 BACKGROUND: Hemophilia B (HB) is an inherited bleeding disorder caused by the absence or dysfunction of coagulation factor IX (FIX). A subset of patients who have HB develop neutralizing alloantibodies (inhibitors) against FIX following infusion therapy. HB prevalence and the proportion of patients who develop inhibitors are much lower than that of hemophilia A (HA), which makes studies of inhibitors in patients with HB challenging due to the limited availability of samples. As a result, there is a knowledge gap regarding HB inhibitors. OBJECTIVE: Evaluate the largest group of inhibitor positive HB patients studied to date to assess the relationship between anti-FIX antibody profiles and inhibitor formation METHODS: A fluorescence immunoassay (FLI) was used to detect anti-FIX antibodies in plasma samples from 37 patients with HB RESULTS: Assessments of antibody profiles showed that anti-FIX IgG1-4 , IgA, and IgE were detected significantly more often in patients with a positive Nijmegen-Bethesda Assay (NBA). All NBA-positive samples were positive for IgG4 . Anti-FIX IgG4 demonstrated a strong correlation with the NBA, while correlations were significant, yet more moderate, for anti-FIX IgG1-2 and IgA CONCLUSIONS: The anti-FIX antibody profile in HB patients who develop inhibitors is diverse and correlates well with the NBA across immunoglobulin (sub)class, and anti-FIX IgG4 is particularly relevant to functional inhibition. The anti-FIX FLI may serve as a useful tool to confirm the presence of antibodies in patients who have low positive NBA results and to more clearly define, predict, and treat alloantibody formation against FIX. |
Characteristics of hemophilia patients with factor VIII inhibitors detected by prospective screening
Miller CH , Rice AS , Boylan B , Payne AB , Kelly FM , Escobar MA , Gill J , Leissinger C , Soucie JM . Am J Hematol 2015 90 (10) 871-6 PURPOSE: To characterize patients with inhibitors identified by prospective screening. FINDINGS: In a prospective study at 17 hemophilia centers with central inhibitor measurement by Nijmegen-Bethesda assay, 23 (2.8%) of 824 hemophilia A patients had new inhibitors detected: 9 high-titer inhibitors (HTI: 7 ≥5.0 NBU plus 2 of 2.6 and 3.4 NBU at immune tolerance induction initiation) and 14 low-titer inhibitors (LTI: 0.5-1.9 NBU). HTI occurred at an earlier age (median 2 years, range 1-18, vs. median 11 years, range 2-61, p=0.016). Both HTI (22%) and LTI (43%) occurred in non-severe patients. All HTI, but only 64% of LTI, were found to be FVIII-specific by chromogenic Bethesda assay or fluorescence immunoassay (FLI), indicating a high rate of false-positive LTI. Repeat specimens confirmed all HTI, 7/9 LTI, and 7/7 FVIII-specific LTI. FLI results were similar between HTI and FVIII-specific LTI; all included IgG1 and IgG4 subclasses. A comparable prospective study conducted from 1975-9 at 13 U.S. centers found 31 (2.3%) new inhibitors among 1360 patients. In both studies, one-third of inhibitors occurred in non-severe patients and one-quarter after 150 exposure days (ED). Significant differences were seen in the age at which inhibitors occurred (median 16 years in the older study vs. 5 years in the current study, p=0.024) and in ED prior to inhibitor development, 10% in the older study and 43% in the current study occurring within 0-20 ED. CONCLUSIONS: Prospective screening detects Inhibitors in patients of all severities, ages, and ED. Some LTI, however, are false positives. |
Evaluation of von Willebrand factor phenotypes and genotypes in Hemophilia A patients with and without identified F8 mutations.
Boylan B , Rice AS , De Staercke C , Eyster ME , Yaish HM , Knoll CM , Bean CJ , Miller CH . J Thromb Haemost 2015 13 (6) 1036-42 BACKGROUND: Hemophilia A (HA) is an X-linked bleeding disorder caused by a deficiency in Factor VIII (FVIII). von Willebrand disease (VWD) is characterized by a quantitative or qualitative defect in von Willebrand Factor (VWF). Patients with VWD with severely low VWF or VWD Type 2N (VWD2N), a VWD subtype distinguished by defective VWF binding to FVIII, may have reduced FVIII levels secondary to their VWD. These patients superficially resemble patients with HA, and pose a potential for misdiagnosis. OBJECTIVES: Investigate the unexplained cause of bleeding in HA patients without known FVIII mutations by assessing plasma VWF antigen (VWF:Ag), FVIII binding capacities, and VWF genotypes. PATIENTS/METHODS: Thirty-seven of 1027 patients with HA studied as part of the Hemophilia Inhibitor Research Study lacked identifiable F8 mutations. These patients (cases) and 73 patients with identified F8 mutations (controls) were evaluated for VWF:Ag, patient's VWF capacity to bind FVIII (VWF:FVIIIB), and VWF sequence. RESULTS: Four cases had VWF:Ag <3 IU/dL and VWF mutations consistent with Type3 VWD. Six cases and one control were heterozygous for mutations previously reported to cause Type1 VWD (VWD1) (n=5 cases and 1 control) or predicted to be deleterious by Polyphen2 and SIFT prediction tools (n=1 case). One control had VWF:Ag <30 IU/dl, and seven patients (4 cases and 3 controls), including two cases who were heterozygous for a known VWD2N mutation, had reduced VWF:FVIIIB. CONCLUSIONS: These data emphasize that some patients diagnosed with HA require VWF assessments in order to achieve a comprehensive diagnosis and an optimal treatment strategy. |
Characterization of the anti-factor VIII immunoglobulin profile in patients with hemophilia A using a fluorescence-based immunoassay
Boylan B , Rice AS , Dunn AL , Tarantino MD , Brettler DB , Barrett JC , Miller CH . J Thromb Haemost 2014 13 (1) 47-53 BACKGROUND: The development of neutralizing antibodies, referred to as inhibitors, against factor VIII (FVIII) is a major complication associated with FVIII infusion therapy for the treatment of hemophilia A (HA). Previous studies have shown that a subset of HA patients and a low percentage of healthy individuals harbor non-neutralizing anti-FVIII antibodies that do not elicit the clinical manifestations associated with inhibitor development. OBJECTIVE: Assess HA patients' anti-FVIII antibody profiles as potential predictors of clinical outcomes. METHODS: A fluorescence immunoassay (FLI) was used to detect anti-FVIII antibodies in 491 samples from 371 HA patients. RESULTS: Assessments of antibody profiles showed that the presence of anti-FVIII IgG1 , IgG2 , or IgG4 correlated qualitatively and quantitatively with the presence of a FVIII inhibitor as reported by the Nijmegen-Bethesda assay (NBA). Forty-eight patients with a negative inhibitor history contributed serial samples to the study, including seven patients who had negative NBA titers initially and later converted to NBA-positive. The FLI detected anti-FVIII IgG1 in five of those seven patients prior to their conversion to NBA-positive. Five of 15 serial-sample patients who had a negative inhibitor history and a positive anti-FVIII IgG1 later developed an inhibitor, compared to 2 of 33 patients with a negative inhibitor history without anti-FVIII IgG1 . CONCLUSIONS: These data provide a rationale for future studies designed both to monitor the dynamics of anti-FVIII antibody profiles in HA patients as a potential predictor of future inhibitor development and to assess the value of the anti-FVIII FLI as a supplement to traditional inhibitor testing. |
Comparison of clot-based, chromogenic, and fluorescence assays for measurement of factor VIII inhibitors in the U.S. Hemophilia Inhibitor Research Study
Miller CH , Rice AS , Boylan B , Shapiro AD , Lentz SR , Wicklund BM , Kelly FM , Soucie JM . J Thromb Haemost 2013 11 (7) 1300-9 BACKGROUND: Detection and validation of inhibitors (antibodies) to hemophilia treatment products are important for clinical care, evaluation of product safety, and assessment of population trends. METHODS: Centralized monitoring for factor VIII (FVIII) inhibitors was conducted for patients in the Hemophilia Inhibitor Research Study using a previously reported modified Nijmegen-Bethesda clotting assay (NBA), a chromogenic Bethesda assay (CBA), and a novel fluorescence immunoassay (FLI). RESULTS: NBA and CBA were performed on 1005 specimens and FLI on 272 specimens. CBA was negative on 880/883 specimens (99.7%) with Nijmegen-Bethesda units (NBU)<0.5 and positive on 42/42 specimens (100%) with NBU≥2.0 and 43/80 specimens (53.8%) with NBU 0.5-1.9. Among specimens with positive NBA and negative CBA, 58.1% were FLI-negative, 12.9% had evidence of lupus anticoagulant, and 35.5% had non-time-dependent inhibition. CBA and FLI were positive on 72.4% and 100% of 1.0-1.9 NBU specimens and 43.1% and 50.0% of 0.5-0.9 NBU specimens. FLI detected antibodies in 98.0% of CBA-positive and 81.6% of NBA-positive specimens (P=0.004). Among 21 new inhibitors detected by NBA, 5 (23.8%) with 0.7-1.3 NBU did not react in CBA or FLI. Among previously positive patients with 0.5-1.9 NBU, 7/25 (28%) were not CBA or FLI positive. FLI was positive on 36/169 NBU-negative specimens (21.3%). CONCLUSIONS: FVIII specificity could not be demonstrated by CBA or FLI for 26% of inhibitors of 0.5-1.9 NBU; such results must be interpreted with caution. Low titer inhibitors detected in clot-based assays should always be repeated, with consideration given to evaluating their reactivity with FVIII using more specific assays. (This article is protected by copyright. All rights reserved.) |
- Page last reviewed:Feb 1, 2024
- Page last updated:Sep 23, 2024
- Content source:
- Powered by CDC PHGKB Infrastructure